Exercise machine, strength evaluation method and pulse rate meter

ABSTRACT

In an exercise machine, when a measurement starts, an electrocardiographic signal is detected by an electrocardiographic sensor  1  (ST 33 ), a load drive is started (ST 4 ), and heartbeat rate intervals of the electrocardiographic signal are sequentially obtained. A fluctuation of heartbeat rate intervals PI(n) % is obtained from a calculation formula in which the RR interval RR(n+1) of the current heartbeat is subtracted from the RR interval RR(n) of the previous heartbeat, which is then divided by RR(n) and multiplied by 100% (ST 5 ). Entropy is calculated from 128 pieces of such PI (ST 6 ). From the change of the entropy under the gradually increasing load (ST 8 ), a minimum point of the entropy is obtained, which point is designated as an anaerobic threshold point (ST 7 ). The load of the exercise machine is controlled employing this anaerobic threshold.

TECHNICAL FIELD

[0001] The present invention relates to an exercise machine, such asbicycle ergometer, treadmill and rowing ergometer, a physical strengthevaluation method and a pulse rate meter.

BACKGROUND ART

[0002] Method and apparatus for determining exertion levels interestedin this invention are disclosed, for example, in InternationalPublication No. WO96/20640. According to the disclosure, heartbeat of aperson engaged in training is monitored. From an electrocardiographicsignal obtained, a QRS complex waveform, for example, is measured tocalculate the heartbeat rate. Based on a power of a spectrum derivedfrom the heartbeat rate, an exertion level of the exercising person isdetermined.

[0003] Further, conventional method and apparatus for measuring muscularendurance of a person engaged in exercise are disclosed, for example, inJapanese Patent Publication No. 7-38885. According to the disclosure, aload of an exercising person is calculated from the product of aheartbeat rate and a blood pressure under vasoconstriction, and from theresult, the muscular endurance is calculated.

[0004] The load of a person engaged in training or exercise hasconventionally been measured as described above. Such measurement hasalso made it possible to estimate the load of an exercising person.

[0005] Conventionally, exercise machines such as a bicycle ergometer andothers have been commercially available for health maintenance andenhancement. In some of such exercise machines, a person inputs his/herage, sex and the like, and an exercise program is arranged according tosuch information based on statistically predetermined exertionintensity. For evaluation of a physical strength level, some machineshave adapted a method of estimating the maximum oxygen intake based on achange of pulsation or the like corresponding to a change of exertionload.

[0006] There is a factor for decision of safe and effective exercise;i.e., an anaerobic threshold (hereinafter, also referred to as “AT”).This threshold value of exertion intensity shows a maximum exertionlevel at which exercise can be done without an abrupt increase of lacticacid in the blood. The AT is conventionally determined employing aninvasive method by taking a blood sample to examine the lactic acidlevel, or in a restraining manner by measuring changes of oxygen andcarbondioxide partial pressures in exhalation by breathing gas analysis.

[0007] Further, for evaluation of physical strength, there areconventionally known methods of estimating maximum oxygen intake,maximum exertion intensity, maximum heartbeat rate and others based on achange of pulsation or the like with respect to the exertion load.

[0008] Such conventional exercise machines and apparatuses fordetermining exertion levels, however, have posed the following problems:

[0009] {circle over (1)} The data obtained from the apparatus and methodfor determining the exertion level has been used only physiologically todetermine the exertion level in training or exercise; the data has notbeen utilized effectively.

[0010] {circle over (2)} Setting of exertion intensity does not conformto working capacity of each person; a sought-after effect cannot beobtained sufficiently from the exercise.

[0011] {circle over (3)} Although the AT is considered most appropriateas the exertion intensity in conformity with the working capacity of theindividual, measurement of the AT is restraining and requires a specialapparatus such as a breathing gas analyzer; such a measuring apparatuscannot practically be mounted on an exercise machine.

[0012] {circle over (4)} The AT, which represents aerobic workingcapacity important for decision of physical strength, cannot bedetermined by or displayed on the exercise machine due to the reasonstated in {circle over (3)} above.

[0013] The present invention is directed to solve the above-describedproblems, and its object is to provide an exercise machine which allowsan exertion level to be readily and accurately found so that the valuecan be used for effective training.

[0014] Another object of the present invention is to provide an exercisemachine which allows an anaerobic threshold to be readily and accuratelyfound so that the value can be used for effective training.

[0015] Yet another object of the present invention is to provide anexercise machine and a physical strength evaluating method which allowphysical strength and exertion levels to be readily found at the sametime, allow a user to understand his/her own working capacity in moredetail to do appropriate exercise, and allow the physical strength andexertion levels to be evaluated with high precision in a time period asshort as possible.

[0016] A still further object of the present invention is to provide apulse rate meter which allows an exertion level to be readily andaccurately found.

DISCLOSURE OF THE INVENTION

[0017] The exercise machine according to the present invention includes:a load device capable of changing a load; a physiological signalmeasuring unit measuring a physiological signal noninvasively over time;an exertion level estimating unit estimating an exertion level based onthe physiological signal corresponding to the change of the load of theload device; and a unit for controlling the load of the load deviceemploying the exertion level estimated.

[0018] The exertion level is estimated based on the physiological signalcorresponding to the change of the load of the load device, and the loadof the load device is controlled to come close to the estimated exertionlevel. Therefore, an exercise machine allowing a user to do appropriateexercise corresponding to his/her own working capacity can be provided.

[0019] Preferably, the exertion level estimating unit estimates theexertion level based on a change of the physiological signal in responseto the change of the load of the load device.

[0020] More preferably, the exertion level estimating unit estimates ananaerobic threshold as the exertion level.

[0021] The exertion level estimating unit estimates the anaerobicthreshold as the exertion level, and the load of the exercise machine iscontrolled based on this threshold value. Thus, an exercise machineallowing a user to do appropriate exercise more efficientlycorresponding to his/her own working capacity can be provided.

[0022] According to an aspect of the present invention, the exertionlevel estimating unit includes a unit for calculating a fluctuation ofheartbeat rate intervals in each electrocardiographic signal detected, aunit for calculating a power of the fluctuation of heartbeat rateintervals and a unit for finding a convergence point of a change of thepower with respect to the increase of the load, and estimates anexertion load corresponding to the convergence point as the exertionlevel.

[0023] The fluctuation of heartbeat rate intervals in theelectrocardiographic signal is calculated and the convergence point ofthe power change of the fluctuation with respect to the load increase isobtained to estimate the exertion level. Thus, an exercise machinecapable of evaluating the exertion level with high precision in a shorttime period can be provided.

[0024] According to another aspect of the present invention, theexercise machine includes: a load device gradually increasing a loadover time; an electrocardiographic sensor detecting anelectrocardiographic signal; a unit for measuring a heartbeat rate ofthe electrocardiographic signal detected while the load is graduallyincreased; a unit for calculating a fluctuation of heartbeat rateintervals in the electrocardiographic signal; an exertion levelestimating unit estimating an exertion level based on the heartbeat rateand the fluctuation of heartbeat rate intervals; a unit for estimatingphysical strength based on a slope of the change of the heartbeat ratewith respect to the change of the load around the exertion levelestimated by the exertion level estimating unit; and a unit forcontrolling the load device to make the load come close to the levelcorresponding to the estimated physical strength.

[0025] The heartbeat rate of the electrocardiographic signal detectedwhile gradually increasing the load is measured, a fluctuation of whichis calculated, and the exertion level is estimated based on theheartbeat rate and the fluctuation of heartbeat rate intervals. The loadof the load device is controlled to come around the estimated exertionlevel. Therefore, an exercise machine allowing a user to understandhis/her own working capacity more precisely and hence to do appropriateexercise can be provided.

[0026] According to a still further aspect of the present invention, thephysical strength evaluating method includes the steps of: graduallyincreasing a load of a load device; detecting by an electrocardiographicsensor an electrocardiographic signal under an increasing exertion loadwhile the load is gradually increased; finding a heartbeat rate and afluctuation of heartbeat rate intervals from the electrocardiographicsignal detected; and estimating physical strength and an exertion levelat the same time from the heartbeat rate and the fluctuation ofheartbeat rate intervals thus obtained.

[0027] The electrocardiographic sensor detects the electrocardiographicsignal corresponding to the increasing exertion load, and the heartbeatrate and the fluctuation of heartbeat rate intervals are obtained fromthe detected electrocardiographic signal. Based on thus obtainedheartbeat rate and fluctuation of heartbeat rate intervals, the physicalstrength and the exertion level are estimated at the same time. Thus, aphysical strength evaluating method capable of evaluating the physicalstrength and the exertion level with high precision in a short timeperiod can be provided.

[0028] According to yet another aspect of the present invention, thepulse rate meter includes: a pulse rate sensor detecting a pulse ratesignal produced by a heart; an alarm unit demanding a gradual increaseof a pitch of exercise; an exertion level estimating unit estimating anexertion level based on the pulse rate signal detected by the pulse ratesensor while exercise is gradually intensified; and a unit for setting apace based on the pitch of exercise corresponding to the exertion levelestimated.

[0029] As the pulse rate meter can estimate the exertion level from thepulse rate signal detected while the pitch of exercise is graduallyincreased, it is possible to readily find an exertion level of anindividual while he/she is engaged in exercise in the field.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030]FIG. 1 is a block diagram showing a circuit configuration of abicycle ergometer according to an embodiment of the present invention.

[0031]FIG. 2 is a perspective view of the bicycle ergometer.

[0032]FIG. 3 illustrates distribution of anaerobic thresholds withrespect to respective maximum heartbeat rates.

[0033]FIG. 4 is a flow chart illustrating a processing operation for ATestimation of the bicycle ergometer of a first example.

[0034]FIGS. 5A and 5B illustrate a gradual load increase by an exercisemachine and an entropy change of fluctuation of heartbeat rateintervals.

[0035]FIG. 6 is a flow chart illustrating an example of an exerciseprogram corresponding to AT.

[0036]FIG. 7 is a flow chart illustrating a processing operation of thebicycle ergometer of a second example.

[0037]FIG. 8 shows a relation between the heartbeat rate and the entropyof fluctuation of heartbeat rate intervals while a load is graduallyincreased in the bicycle ergometer of the second example.

[0038]FIG. 9 shows a relation between the load and the heartbeat ratewhile the load is gradually increased in the bicycle ergometer of thesecond example.

[0039]FIG. 10 shows, in a worn state, one of the electrocardiographicsensors being used in the bicycle ergometers of the first and secondexamples.

[0040]FIG. 11 shows another electrocardiographic sensor being used inthe bicycle ergometer of the first example.

[0041]FIG. 12 shows yet another electrocardiographic sensor being usedin the bicycle ergometers of the first and second examples.

[0042]FIG. 13 shows, in a worn state, a pulse rate sensor being used inthe bicycle ergometer according to the first embodiment.

[0043]FIGS. 14A and 14B each show, in a worn state, a blood pressuregauge for finger being used in the bicycle ergometer according to thefirst embodiment.

[0044]FIGS. 15A and 15B illustrate a way of detecting the breathing rateemployed in the bicycle ergometer according to the first embodiment.

[0045]FIG. 16 is a perspective view of a treadmill as another example ofthe exercise machine implementing the present invention.

[0046]FIG. 17 shows a rowing ergometer as a further example of theexercise machine implementing the present invention.

[0047]FIG. 18 is a flow chart showing contents of processing accordingto a second embodiment, for controlling a load by calculating a power offluctuation of heartbeat rate intervals.

[0048]FIGS. 19A and 19B show a relation between the load and the powerof fluctuation.

[0049]FIG. 20 is a block diagram showing a configuration of a pulse ratemeter according to a fourth embodiment.

[0050]FIG. 21 illustrates how a heartbeat rate meter according to thefourth embodiment is worn by a test subject.

[0051]FIG. 22 is a flow chart showing a processing operation of theheartbeat rate meter according to the fourth embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0052] Hereinafter, embodiments of the present invention will bedescribed with reference to the drawings.

[0053] (1) First Embodiment

[0054]FIG. 1 is a block diagram showing a circuit configuration of abicycle ergometer that is an example of the exercise machine accordingto the first embodiment of the present invention. This ergometerincludes an electrocardiographic sensor 1 detecting anelectrocardiographic signal; a preamplifier 2 amplifying the outputsignal; a filter 3 removing noise; an amplifier 4 further amplifying theelectrocardiographic signal to an appropriate level, an A/D converter 5;a CPU 6 performing various kinds of processing; a key input device 7; adisplay 8; and a load device (applying a rotation load) 9.

[0055]FIG. 2 is a perspective view of the bicycle ergometer according tothis embodiment. Referring to FIG. 2, the bicycle ergometer includes: asaddle 11; a handle 12; a manipulation unit 13; pedals 14; a front footframe 15; and a hind foot frame 16. Manipulation unit 13 includes keyinput device 7 and display 8 (See FIG. 1). With this ergometer, a testsubject (an exercising person) sits on saddle 11 and works pedals 14 torotate them for exercise. Load device 9 applies a load to pedals 14 togive them weight corresponding to a degree of exertion intensity. Forthe greater load, the larger amount of exercise is naturally needed torotate pedals 14 a fixed number of times. Electrodes ofelectrocardiographic sensor 1 are attached to the chest of the subjectby means of a belt. The electrocardiographic to signal detected istransmitted by radio to manipulation unit 13 and other circuits forprocessing.

[0056]FIG. 10 illustrates an example of how electrocardiographic sensor1 is worn. A chest belt 41 incorporating a pair of electrodes and atransmitter is worn around the chest of the subject M. Handle 12incorporates a receiver (corresponding to manipulation unit 13 of FIG.2) 42.

[0057]FIG. 11 shows another example of the electrocardiographic sensorfor use with the bicycle ergometer. Electrodes 43, 44 forelectrocardiographic detection are provided in handle 12. Gripping thehandles, and hence, electrodes 43, 44 with respective hands enables theelectrocardiographic detection. Electrodes 43, 44 are connected to thecircuitry within the body of ergometer.

[0058]FIG. 12 illustrates still another example of theelectrocardiographic sensor used with the bicycle ergometer. Referringto FIG. 12, three electrodes 45, 46, 47 of G (ground),+ (plus) and −(minus), respectively, are attached to the chest of the exercisingperson M. This sensor is of a chest leads type with the electrodes beingconnected to the circuitry within the ergometer body by wire 48 fordetection of the electrocardiographic signal.

[0059]FIG. 13 shows an example of a pulsation sensor for use with thebicycle ergometer. The pulsation sensor 49 is attached to an earlobe ofthe subject M for detection of pulsation.

[0060] In a conventional exercise machine such as an ergometer, anexercise program for weight reduction or enhancement of physicalstrength was determined based on the statistic data stating that the ATpoint as an example of exertion level should be around 55% of themaximum heartbeat rate (maximum exertion intensity) determined by age orthe like having been input.

[0061] In practice, however, the actual measurement of AT represented in% as a ratio to the maximum heartbeat rate greatly differs from personto person, as shown in FIG. 3. FIG. 3 shows distribution of the ATmeasurements of 24 male students, with their respective maximumheartbeat rates being 100%. Thus, the exercise program based on theexertion intensity statistically determined in the conventional manneris not necessarily best suited for each person.

[0062] In the bicycle ergometer according to the present embodiment, inaddition to the conventionally displayed physical strength level that isshown by estimating the maximum exertion intensity such as the maximumoxygen intake (maximum heartbeat rate), an AT as an example of exertionlevel is estimated at the same time from a fluctuation of heartbeat rateintervals, and is output for display as aerobic working capacity.

[0063] Now, the processing operation of the bicycle ergometer accordingto the present embodiment will be described with reference to the flowchart shown in FIG. 4. When measurement start key depress information isinput from key input device 7 to CPU 6, the measurement is started.First, an electrocardiographic signal at rest is detected byelectrocardiographic sensor 1 (step ST1; hereinafter “step” is notrepeated). A calibration operation is performed so that this signal fromelectrocardiographic sensor 1 reaches a certain fixed level (ST2). Toaccomplish this calibration operation, a gain is adjusted at amplifier 4according to a signal from CPU 6.

[0064] “Start measurement” is displayed on display 8 (ST3), and loadcontrol of load device 9 is started (ST4). As the load of load device 9,a ramp load of 15 W [watt] per minute is applied. The peak value of theelectrocardiographic signal is detected to obtain RR interval data (onecycle of heartbeat). Using thus obtained RR data, PI (Percent Index) iscalculated (ST5). Herein, the PI represents, in percentage, a ratio of adifference between the previous cycle and the current cycle to theprevious cycle, which is calculated from the following expression:

PI(n)%={RR(n)−RR(N+1)}/RR(n)×100%

[0065] Herein, this PI is called a fluctuation of heartbeat rateintervals.

[0066] From 128 pieces of this PI data, or at an interval of every twominutes, frequency distribution in percentage is calculated. FromP(i)=f(i)/f, and according to the following expression (1), entropy H ofthe fluctuation of heartbeat rate intervals is calculated (ST6).$\begin{matrix}{H = {- {\sum\limits_{i}{{P(i)}\log_{2}{P(i)}}}}} & (1)\end{matrix}$

[0067] Thereafter, a decision is made whether the AT point is reached(ST7). As shown in FIGS. 5A and 5B, if the entropy decreases as theamount of exercise increases, the decision is NO. The load is thusincreased gradually (ST8), while the PI value and entropy are calculatedcontinuously (ST5, ST6). As shown in FIG. 5A, when the entropy reachesits polarization point (minimum point), the point is regarded as the ATpoint. Thus, the decision in ST7 is YES, and this result is displayed ondisplay 8 (ST9). The result includes heartbeat rate (bPM), loadintensity (W), time (min) or the like at the AT point. After the displayof the result, the load is decreased for cooling down (ST10). After oneminute of the cooling down, application of the load is stopped, and thecontrol is terminated (ST11).

[0068] The bicycle ergometer according to the present embodiment has acapability to readily obtain the AT. Conventionally, the exertionintensity of the exercise program for weight reduction, enhancement ofphysical strength or the like was set as its ratio to the maximumheartbeat rate in percentage, e.g., 65% for weight reduction, and 75%for physical strength enhancement. Conversely, with the presentembodiment, such exertion intensity can be set like 18% less or 18%greater than the AT point. Thus, it becomes possible to adjust theexertion intensity to conform to the exertion level of the individual.

[0069]FIG. 6 is a flow chart showing an example of the process todetermine exertion intensity from an estimated AT in the exercisemachine according to the present embodiment. When the AT point isestimated (ST21), or, if the AT value of the specific person is alreadyknown and it is input via key input device 7 (ST22), then adetermination is made whether a weight reduction program is designated(ST23). If YES, the load is set to 82% of the AT (ST24). If the weightreduction program is not designated, a determination is further madewhether a physical strength enhancement program is designated (ST25). IfYES, the load is set to 118% of the AT (ST26). If NO in ST25, controlgoes to still another process.

[0070] The bicycle ergometer according to the present embodiment is ableto readily estimate both the maximum heartbeat rate (exertion intensity)and the AT. Thus, by showing in percentage a ratio of AT to the maximumheartbeat rate (exertion intensity) for each person, it is possible toshow aerobic working capacity of the person in relation to a statisticalaverage level. Thus, with this exercise machine having such a displayoutput capability, not only the simple physical strength level, but alsothe aerobic working capacity can be output for display, so that a usercan readily know his/her aerobic working capacity that has never beenknown with ease.

[0071] Another example of the ergometer according to the presentembodiment will be described. The bicycle ergometer of this example hasa circuit configuration similar to the one shown in FIG. 1, and again,in addition to the conventional display of physical strength levelprovided based on the estimation of the maximum exertion intensity suchas the maximum oxygen intake (maximum heartbeat rate), it can estimate,at the same time, the AT from the fluctuation of heartbeat rateintervals, and output it for display as the aerobic working capacity.

[0072] The entire operation of the exercise machine of this example willbe described with reference to the flow chart shown in FIG. 7. Where theoperation starts, personal data, such as age, sex or the like, isentered via key input device 7 (ST31). Next, a determination is madewhether only the AT is to be estimated (ST32). If so with only theestimation of AT having been designated via key input device 7, entropy,of a heartbeat rate fluctuation at rest is calculated (ST33). If thisentropy level is less than 2.0, it is determined that the AT estimationis impossible, and the estimation is terminated (ST35). This is becausesome test subjects exhibit almost no heartbeat rate fluctuation andhence a low entropy level at rest, and therefore, even if they aresubjected to an exertion load test, the AT determination is expected tobe very difficult. Thus, it is determined in advance that the ATestimation is impossible for them, such that they need not dounnecessary exercise.

[0073] For a test subject with the entropy level at least 2, or for asubject requesting estimation of both the AT and the physical strength,the heartbeat rate at rest is measured (ST36) and the exertion load testis conducted. At this time, an initial load value and an exertion loadpattern of, e.g., gradually increasing ramp load are determined based onthe personal data (ST37, ST38). Specifically, as it is inefficient touse the same pattern for persons with different physical strengthlevels, the personal data including age, sex or the like is referred to,and, for a subject with high physical strength level, initial values ofthe exertion load level and of a load increasing rate are set high. Itshould be understood, however, in order to maintain high precision inestimation, the load increasing rate exceeding a certain level, e.g., 40W/min, is not applied in this case.

[0074] After the exertion load test, the physical strength and the ATlevel are estimated (ST39). Thereafter, a determination is made whetherthe AT estimation was possible (ST40). If the AT estimation was notpossible, a statistical AT level, for example, 55% of the maximumheartbeat rate, is estimated from the estimated physical strength level(maximum heartbeat rate) (ST41), and output with the physical strengthlevel (ST42). If it was possible to estimate the AT in ST40, thusestimated AT level and the physical strength level are likewise output(ST42).

[0075] The above-described tests of physical strength and AT areconducted as follows. For the AT, the heartbeat rate interval dataobtained by the exertion load test is used to find a relation betweenthe heartbeat rate and the entropy of the fluctuation of heartbeat rateintervals as shown in FIG. 8. The AT is obtained as a heartbeat rate atthe minimum point of the entropy.

[0076] To obtain the entropy of the heartbeat rate fluctuation, the PIis first calculated using the RR data and the following expression (2).

PI(n)%={RR(n)−RR(n+1)}/R(n)×100   (2)

[0077] From 128 pieces of such PI data, or at an interval of every twominutes, frequency distribution in percentage is calculated. P(i)=fi/fis then found, and the entropy H is calculated using the expression (1)explained in conjunction with FIG. 4.

[0078] Next, the physical strength level corresponding to the maximumexertion intensity is estimated based on the estimated AT, by finding aslope of the heartbeat rate change with respect to the exertion loadlevel (W) within a predetermined range of, e.g., ±20 beats around theheartbeat rate at the estimated AT level, as shown in FIG. 9. If the ATestimation was not possible, a similar estimation is carried out in arange of ±20 beats around an index that is determined by{(200−age)−heartbeat rate at rest}×0.55+heartbeat rate at rest.

[0079] Accordingly, it is possible to estimate, from theelectrocardiographic signal obtained at the exertion load test, the ATand the physical strength simultaneously and efficiently in a leastpossible time period.

[0080] Each example described above has used the electrocardiographicsignal measured by the electrocardiographic sensor as a physiologicalsignal, and has employed the fluctuation of heartbeat rate intervals forestimation. Instead of the electrocardiographic signal, DP (DoubleProduct) (blood pressure×heartbeat rate) or a breathing rate may be usedas the physiological signal. The blood pressure during exercise can bemeasured, for example, by contacting handle 12 of the bicycle ergometerwith a cuff 50 of a blood pressure gauge for finger, as shown in FIGS.14A, 14B. In FIG. 14B, 51 denotes an air tube with a pulse signal line52. The heartbeat rate can of course be measured by various kinds ofelectrocardiographic sensors as described above. The breathing rate ismeasured by attaching a thermistor 53 to the nose of the exercisingperson M. Thermistor 53, which is held, for example, by a tape 54widening the nostril (see FIG. 15B), detects the temperature change dueto breathing to measure the breathing rate.

[0081] In addition, although the bicycle ergometer has been used as theload device capable of changing a load in each example described above,the present invention is also applicable to a treadmill as shown in FIG.16, a rowing ergometer in FIG. 17, or the like.

[0082] Referring to FIG. 16, a running belt is denoted by 21. Amanipulation unit 22 includes a display portion, a key input portion andthe like. When a power supply switch 23 is turned on, a built-in motorstarts to move running belt 21. A person about to do exercise gets onthis running belt 21, adjusts the moving rate of the belt, and startsrunning. In this treadmill, changing the number of rotation of the motoror the angle of inclination of the running belt can change the load.

[0083] The rowing ergometer shown in FIG. 17 includes a seat 31, a rail32, a power supply switch 33, a foot rest 34, a bar 35 and amanipulation panel 36. A person about to do exercise sits on seat 31 andpulls the bar 35 with a rope attached thereto close to him/her andreturns it back to its initial position repeatedly, so that he/she cando exercise feeling the load power incorporated. In this rowingergometer, changing the tensile force of the bar that works to let itreturn to its initial position can alter the load.

[0084] (2) Second Embodiment

[0085] Hereinafter, the second embodiment of the present invention willbe described. In the second embodiment, the anaerobic threshold isestimated utilizing a power of the fluctuation of heartbeat rateintervals. A bicycle ergometer being used and data being obtained from atest subject in the second embodiment are similar to those in the firstembodiment.

[0086]FIG. 18 is a flow chart showing contents of electrocardiographicsignal processing according to the second embodiment. Referring to FIG.18, in this embodiment, the electrocardiographic signal at rest is firstdetected (ST51). Calibration is then conducted, start of measurement isdisplayed, and load control is started (ST52-ST54). The steps heretoforeare the same as in the first embodiment.

[0087] In the second embodiment, the peak of the electrocardiographicsignal from eletrocardiographic sensor 1 is detected, and RR intervaldata (one cycle of the heartbeat rate) is calculated. Based on the RRinterval data, a power is calculated using the following expression (3):

power(n)[ms ² ]={RR(n−1)−RR(n)}²   (3)

[0088] That is, the power is the square of the difference between theprevious RR interval and the current RR interval. Herein, this power iscalled a power of the fluctuation of heartbeat rate intervals. Theaverage value of this power data for 30 seconds, detected in 15 seconds,is used for estimation of the anaerobic threshold as an example of theexertion level.

[0089] Next, in ST56, a determination is made whether the AT point hasbeen reached. FIGS. 19A and 19B illustrate changes of the power of thefluctuation and the load over time. As shown in FIGS. 19A and 19B, thepower of the fluctuation decreases to converge as the exertion loadincreases. The convergence point of the curved line showing thevariation in the power of the fluctuation corresponds to the AT point.Herein, the convergence point is determined so when the power of thefluctuation becomes lower than a predetermined bottom value and when thedifference from the previous power value (power (n−1)−power (n): slopeof the curved line showing the variation of the fluctuation power)becomes lower than a predetermined reference value.

[0090] The load is increased until the AT point is obtained (ST57). Whenthe anaerobic threshold point is reached (YES in ST56), the result isdisplayed, the load is decreased, and the load control is terminated(ST58-ST60). These steps are again the same as those in the firstembodiment.

[0091] (3) Third Embodiment

[0092] Now, the third embodiment of the present invention will bedescribed. A load of exercise may be controlled employing an oxygenintake, which is calculated from a load upon appearance of the anaerobicthreshold detected by a method of either the first or the secondembodiment. The oxygen intake (VO2) is calculated from the load at thetime of appearance of the AT using a conversion formula, and VO2 per 1kilogram of weight is obtained.

[0093] For example, when a person weighing 70 kg exercises with abicycle ergometer and the AT appears at 100W, then the oxygen intake 13calculated by the following expression (4):

VO2 (ml/kg/min)=load(W)÷0.232×14.3÷5.0÷weight(kg)   (4)

[0094] Herein, 0.232 means that the exercise efficiency of the bicycleergometer is 23.2%. 14.3 is a conversion coefficient of 1 watt=14.3cal/min. 5.0 is a conversion coefficient meaning that 5.0 kcal isconsumed with the oxygen consumption of 1 litter. The operation resultis as follows:

VO2 (ml/kg/min)=100÷0.232×14.3÷5.0÷7.0=17.6

[0095] This means that the VO2 at the time of appearance of theanaerobic threshold is 17.6 (ml/kg/min).

[0096] As the AT of a healthy person generally appears at about 55% ofthe maximum oxygen intake (VO2max), the physical strength is measured byregarding the 55% of the standard value of VO2max at each age as thestandard value of the anaerobic threshold.

[0097] (4) Fourth Embodiment

[0098] Now, the fourth embodiment of the present invention will bedescribed. In the fourth embodiment, the method of detecting theanaerobic threshold as an example of the exertion level described in thefirst through third embodiments is applied to a pulse rate meter such asa heartbeat rate meter.

[0099] The configuration of the heartbeat rate meter according to thepresent embodiment is shown in FIG. 20. Referring to FIG. 20, theheartbeat rate meter of this embodiment includes: a heartbeat ratesensor 61; a preamplifier 62 amplifying a heartbeat rate signal detectedby heartbeat rate sensor 61; a filter 63 removing noise; an amplifier 64further amplifying the heartbeat rate signal amplified and filtered; anA/D converter 65; a CPU 66 performing various kinds of processingincluding estimation of an anaerobic threshold; a key input device 67; adisplay 68; a memory 69; and an alarm 70.

[0100] With the heartbeat rate meter according to the presentembodiment, when the heartbeat rate reaches the AT level, alarm 70notifies that it is at the anaerobic threshold level. Display 68displays the same information. Display 68 and alarm 70 also designate apace of exercise at the anaerobic threshold level. Further, an exercisetime with exertion intensity within a target zone that is set on thebasis of the anaerobic threshold, and an exercise time with exertionintensity stronger or weaker than the exertion intensity in this rangeare calculated, and also displayed on display 68. The respectiveexercise times are stored in memory 69.

[0101]FIG. 21 shows, by way of example, how the heartbeat rate meteraccording to the present embodiment is worn. This heartbeat rate meteris formed of an enclosure 71 and a body 72 in the form of a wristwatch.Enclosure 71 includes electrocardiographic electrodes 73 and atransmitter 74, and body 72 receives the heartbeat rate signaltransmitted. In terms of the circuit configuration, a transmitting unitand a receiving unit are provided anywhere between preamplifier 62 andA/D converter 65 shown in FIG. 20. Although body 72 is shown in the formof wristwatch, it may be a box having a manipulation panel or the like,dependent on a type of exercise.

[0102] Now, the processing operation of the heartbeat rate meteraccording to the present embodiment will be described with reference tothe flow chart shown in FIG. 22. When start key depress information isinput from key input device 7 to CPU 6, the measurement is started, anda determination is first made whether it is an AT input mode (ST71). Ifso, the AT pitch previously determined or the like is input, or read outfrom memory 69 (ST77). Thereafter, step ST76 and subsequent steps arecarried out, which will be described later.

[0103] In ST71, if it is not the AT input mode and if the AT should beestimated, then a rest state is designated by alarm 70, and theheartbeat rate data at rest is input to CPU 66. At this time,calibration is performed such that the signal from heartbeat rate sensor61 attains a prescribed fixed level (ST72).

[0104] Next, alarm 70 demands an exercise at a pitch corresponding tothat of walking. The heartbeat rate data at this time is taken into CPU6. The anaerobic threshold is then estimated (ST73). For this estimationof the anaerobic threshold, the pitch is gradually increased, and thecorresponding heartbeat rate data are taken into CPU 66. The RR intervaldata is extracted, and then, the PI is calculated. Here, the PI iscalculated by the expression (2) described above.

[0105] From 128 pieces of the PI data, or at an interval of every twominutes, frequency distribution in percentage is calculated. FromP(i)=f(i)/f, according to the expression 2 as in the first embodiment,the minimum point of the entropy is detected and the anaerobic thresholdis estimated (ST73, ST74).

[0106] The heartbeat rate and the pitch at this time are stored as theAT heartbeat rate and the AT pitch in memory 69, while they aredisplayed on display 68 and notified by alarm 70 (ST75).

[0107] Next, the AT pitch is used to set a pace of exercise. This paceof exercise is designated via display 68 and alarm 70 (ST76). Adetermination is then made whether the exercise is being done with theexertion intensity within a target zone that is set based on the ATpitch, or it is being done with the exertion intensity stronger orweaker than that in this range (ST78). According to the determination,“appropriate” (ST79), “strong” (ST80) or “weak” is displayed (ST81).Exercise times corresponding to respective exertion intensities arestored in memory 69 and displayed on display 68 (ST82). Alternatively,they may be only displayed on display 68 or only stored in memory 69.

[0108] In the heartbeat rate meter shown in FIG. 21, if a pulse ratesensor 61 a is used in place of heartbeat rate sensor 61, it becomes apulse rate meter, which can be utilized in the same manner as theheartbeat rate meter.

[0109] In the fourth embodiment, entropy is used for detection of theanaerobic threshold. Not limited thereto, however, the anaerobicthreshold may also be detected employing the second or third embodiment.

[0110] Further, in the embodiments above, the anaerobic threshold hasbeen used as the exertion level. Not limited thereto, however, theexertion level may of course be obtained employing any other data aslong as it is based on the change of a physiological signalcorresponding to the change of a load of the load device.

[0111] Industrial Applicability

[0112] As explained above, the exercise machine according to the presentinvention estimates the anaerobic threshold based on anelectrocardiographic signal corresponding to the change of a load of theload device, and controls the load based on the estimated value. Thus,an exercise machine permitting each person to do appropriate exercise inconformity with his/her own physical strength can be provided.

1. An exercise machine comprising: a load device capable of changing aload; a physiological signal measuring unit measuring a physiologicalsignal noninvasively over time; an exertion level estimating unitestimating an exertion level based on the physiological signalcorresponding to a change of the load of said load device; and achanging unit for changing the load of said load device employing theexertion level estimated.
 2. The exercise machine according to claim 1,wherein said exertion level estimating unit estimates the exertion levelbased on a change of said physiological signal in response to the changeof the load in said load device.
 3. The exercise machine according toclaim 2, wherein said exertion level estimating unit estimates ananaerobic threshold as said exertion level.
 4. The exercise machineaccording to any of claims 1-3, wherein said load device is capable ofgradually increasing the load over time, said physiological signalmeasuring unit is an electrocardiographic sensor detecting anelectrocardiographic signal, and said exertion level estimating unitestimates the exertion level based on the electrocardiographic signaldetected while said load is gradually increased.
 5. The exercise machineaccording to claim 4, wherein said electrocardiographic sensor detectsthe electrocardiographic signal from an electrode provided in a gripportion.
 6. The exercise machine according to claim 4, wherein saidelectrocardiographic sensor includes a pair of electrodes and atransmitter provided in a chest belt.
 7. The exercise machine accordingto claim 4, wherein said electrocardiographic sensor is of a chest leadstype in which an electrode is attached to a chest of an exercisingperson by an adhesive material.
 8. The exercise machine according toclaim 4, wherein said exertion level estimating unit estimates saidanaerobic threshold based on a fluctuation of heartbeat rate intervalsin each electrocardiographic signal detected.
 9. The exercise machineaccording to claim 4, wherein said exertion level estimating unitincludes a unit for calculating the fluctuation of heartbeat rateintervals in each electrocardiographic signal detected, a unit forcalculating entropy of the fluctuation of heartbeat rate intervals, anda unit for finding a minimum point of a characteristic change of theentropy with respect to an increase of the load, and estimates a loadcorresponding to the minimum point as the anaerobic threshold.
 10. Theexercise machine according to any of claims 1-3, wherein saidphysiological signal measuring unit includes a blood pressure measuringunit and an electrocardiographic sensor, and said exertion levelestimating unit estimates the exertion level by multiplying the bloodpressure by the heartbeat rate.
 11. The exercise machine according toany of claims 1-3, wherein said physiological signal measuring unitincludes a breathing sensor, and said exertion level estimating unitestimates the exertion level based on the breathing rate.
 12. Theexercise machine according to claim 4, wherein said exertion levelestimating unit includes a unit for calculating a fluctuation ofheartbeat rate intervals in each electrocardiographic signal detected, aunit for calculating a power of the fluctuation of heartbeat rateintervals, and a unit for finding a convergence point of a change of thepower with respect to an increase of the load, and estimates an exertionload corresponding to said convergence point as the exertion level. 13.The exercise machine according to any of claims 1-4 comprising a unitfor inputting an exertion level, wherein said changing unit for changingthe load of the load device can also determine the exertion level basedon the input exertion level.
 14. The exercise machine according to anyof claims 1-4, comprising a unit for determining an exercise programbased on said exertion level and a unit for outputting the exerciseprogram determined.
 15. The exercise machine according to claim 14,wherein a pitch or load is altered so that the exercise is proceededaccording to said exercise program.
 16. The exercise machine accordingto any of claims 1-4 or 13-15, wherein aerobic working capacity isevaluated based on a ratio, in percentage, of the estimated exertionlevel to a maximum heartbeat rate.
 17. An exercise machine, comprising:a load device gradually increasing a load over time; anelectrocardiographic sensor detecting an electrocardiographic signal; aunit for measuring a heartbeat rate of the electrocardiographic signaldetected while the load is gradually increased; a unit for calculating afluctuation of heartbeat rate intervals in the electrocardiographicsignal; an exertion level estimating unit estimating an exertion levelbased on said heartbeat rate and said fluctuation of heartbeat rateintervals; and a unit for controlling the load of the load device basedon the exertion level estimated.
 18. The exercise machine according toclaim 17, wherein said exertion level is an anaerobic threshold.
 19. Theexercise machine according to any of claims 1-4 or 13-15, whereinaerobic working capacity is evaluated from an estimated value of oxygenintake at the exertion level estimated.
 20. An exercise machine,comprising: a load device gradually increasing a load over time; anelectrocardiographic sensor detecting an electrocardiographic signal; aunit for measuring a heartbeat rate of the electrocardiographic signaldetected while the load is gradually increased; a unit for calculating afluctuation of heartbeat rate intervals in the electrocardiographicsignal; an exertion level estimating unit estimating an exertion levelbased on said heartbeat rate and said fluctuation of heartbeat rateintervals; and a unit for estimating physical strength from a slope of achange of the heartbeat rate with respect to the change of the loadaround the exertion level estimated.
 21. The exercise machine accordingto claim 20, wherein said exertion level is an anaerobic threshold. 22.The exercise machine according to claim 21, wherein, if said exertionlevel estimating unit is unable to estimate the exertion level based onthe fluctuation of heartbeat rate intervals, the exertion level isestimated and output based on other physiological information orphysical information of a test subject.
 23. The exercise machineaccording to any of claims 17-20, comprising a determination unit fordetermining whether estimation of the exertion level is performed or nottaking into account a degree of said fluctuation of heartbeat rateintervals at rest.
 24. The exercise machine according to any of claims17-20, wherein said exertion level estimating unit conducts an exertionload test based on an initial value of the exertion load that iscalculated from personal data including age, sex of a test subject. 25.The exercise machine according to any of claims 17-20 or 24, whereinsaid exertion level estimating unit estimates the exertion level whilethe load of said load device is gradually increased at a speed lowerthan a prescribed speed.
 26. A method of evaluating physical strength,comprising the steps of: gradually increasing a load of a load device;detecting an electrocardiographic signal by an electrocardiographicsensor under an increasing exertion load while the load is graduallyincreased; finding a heartbeat rate and a fluctuation of heartbeat rateintervals from the electrocardiographic signal detected; andsimultaneously estimating physical strength and an exertion level fromthe heartbeat rate and fluctuation of heartbeat rate intervals thusfound.
 27. The physical strength evaluating method according to claim26, wherein said exertion level is an anaerobic threshold.
 28. A pulserate meter, comprising: a pulse rate sensor detecting a pulse ratesignal produced by a heart; an alarm unit demanding a gradual increaseof a pitch of exercise; an exertion level estimating unit estimating anexertion level based on the pulse rate signal detected by the pulse ratesensor while exercise is gradually intensified; and a unit for setting apace based on the pitch of exercise upon estimation of said exertionlevel.
 29. The pulse rate meter according to claim 28, wherein saidexertion level estimating unit estimates the exertion level based on achange of said pulse rate signal.
 30. The pulse rate meter according toclaim 29, wherein said estimated exertion level is an anaerobicthreshold.
 31. The pulse rate meter according to any of claims 28-30,wherein said exertion level can be input using an input device.
 32. Thepulse rate meter according to any of claims 28-30, wherein said exertionlevel estimating unit estimates the exertion level based on afluctuation of pulse rate intervals.
 33. The pulse rate meter accordingto any of claims 28-30, wherein said exertion level estimating unitincludes a unit for calculating a fluctuation of pulse rate intervals ineach pulse rate signal detected, a unit for calculating entropy of thefluctuation of pulse rate intervals and a unit for finding a minimumpoint of a characteristic change of the entropy with respect to theexercise being intensified, and estimates a load corresponding to theminimum point as the exertion level.
 34. The pulse rate meter accordingto any of claims 28-30, 32 or 33, comprising an alarm unit notifying ofcompletion of estimation by said exertion level estimating unit upon thecompletion.
 35. The pulse rate meter according to any of claims 28-33,wherein said estimated exertion level is output for display.
 36. Thepulse rate meter according to any of claims 28-35, comprising a unit fordesignating, when said exertion level is reached by graduallyintensifying the exercise, a pace of exercise corresponding to theexertion level.
 37. The pulse rate meter according to any of claims28-36, comprising a unit for calculating an exercise time with exertionintensity within a target zone that is set based on said exertion leveland an exercise time at exertion intensity that is stronger or weakerthan the exertion intensity within the target zone, a unit fordisplaying the exercise times, and/or a unit for storing the exercisetimes.
 38. The exercise machine according to any of claims 28-30,wherein said exertion level estimating unit includes a unit forcalculating a fluctuation of heartbeat rate intervals in eachelectrocardiographic signal detected, a unit for calculating a power ofthe fluctuation of heartbeat rate intervals and a unit for finding aconvergence point of a change of the power with respect to an increaseof the load, and estimates an exertion load corresponding to saidconvergence point as the exertion level.